Frontal Cortical and Subcortical Projections Provide a Basis for Segmenting the Cingulum Bundle: Implications for Neuroimaging and Psychiatric Disorders

Abstract

The cingulum bundle (CB) is one of the brain's major white matter pathways, linking regions associated with executive function, decision-making, and emotion. Neuroimaging has revealed that abnormalities in particular locations within the CB are associated with specific psychiatric disorders, including depression and bipolar disorder. However, the fibers using each portion of the CB remain unknown. In this study, we used anatomical tract-tracing in nonhuman primates (Macaca nemestrina, Macaca fascicularis, Macaca mulatta) to examine the organization of specific cingulate, noncingulate frontal, and subcortical pathways through the CB. The goals were as follows: (1) to determine connections that use the CB, (2) to establish through which parts of the CB these fibers travel, and (3) to relate the CB fiber pathways to the portions of the CB identified in humans as neurosurgical targets for amelioration of psychiatric disorders. Results indicate that cingulate, noncingulate frontal, and subcortical fibers all travel through the CB to reach both cingulate and noncingulate targets. However, many brain regions send projections through only part, not all, of the CB. For example, amygdala fibers are not present in the caudal portion of the dorsal CB. These results allow segmentation of the CB into four unique zones. We identify the specific connections that are abnormal in psychiatric disorders and affected by neurosurgical interventions, such as deep brain stimulation and cingulotomy.

Altered White Matter Diffusivity of the Cingulum Angular Bundle in Posttraumatic Stress Disorder

“…Moreover, associations have been reported between CAB integrity and functioning in episodic memory, decision-making, and executive control [42,43]. The CAB has also been shown to directly connect the posterior cingulate cortex and the subiculum of the hippocampus [44], both of which are critical nodes in the default mode network shown to be altered in PTSD [1,45]. The CAB connects the hippocampus and other regions of the medial temporal lobe with the posterior cingulate [43], an area that has been shown to exhibit alterations of gray matter integrity (thinning) in this group of participants [30].…”

Economic Choice as an Untangling of Options into Actions

“…In many cases, connectivity is organized along large trans-areal gradients or is patchy (e.g. Averbeck et al, 2014; Heilbronner and Haber, 2014). These facts pose a challenge to area/function mapping.…”

Neurobiological underpinnings of bipolar disorder focusing on findings of diffusion tensor imaging: a systematic review

“…These regions have been extensively related to the pathophysiology of BD. [67][68][69] In projection fibers, three studies described decreased FA values in the ATR. The ATR connects the dorsomedial and anterior thalamic nuclei with the prefrontal cortex, and the anterior part of the ATR is connected with the hippocampus through the fornix.…”